A computer network is a collection of interconnected subnetworks that transmit data between network nodes. A network node is any device capable of sending or receiving data in the network.
Internet Protocol (IP) specifies the exact format of all data as it travels through the network, performs routing functions and selects the transmission path on which data will be sent. Typical routing takes the shortest path in a network even when those paths are congested. Routers utilize ports and addresses in routing tables to send data packets or cells through the network from node to node.
Multiprotocol Label Switching (MPLS) is a general-purpose tunneling mechanism that uses label switching to forward data packets or cells. MPLS, unlike IP, allows packets sent between two nodes to take different paths based on different MPLS labels. MPLS makes use of label-switched paths (LSPs) to steer traffic over certain routes. Service providers can specify explicit routes by using Resource Reservation Protocol-Traffic Engineering (RSVP-TE).
As MPLS becomes more economical in the access ring network to support such services as Triple Play and Mobility, a bandwidth efficient means of handling traffic reroute in case of network failures will become more important. The current RSVP-TE implementation of Fast Reroute (FRR) on a protected LSP is very bandwidth inefficient in such a ring topology.
In a MPLS network, when local failure triggers a node to FRR protect LSP, the node Point of Local Repair (PLR) will send traffic received from the headend (HE) node into the bypass tunnel to reach the tailend (TE) node of the protected LSP. In a ring topology, this bypass tunnel will traverse all the way back to the HE node of the LSP and then reach the TE node from the opposite direction of the original protected LSP path. This causes traffic to flow to the PLR node and then to return in the bypass tunnel, which generates unnecessary congestion in the ring and reduces the bandwidth efficiency of the ring.
Because FRR is currently designed to reduce the convergence time to the network failure assuming that the most efficient way of protecting traffic is to repair the path as close as possible to the failure point and merge the path back to the original path as early as possible, the current implementation of FRR causes the traffic to travel from HE node to the PLR node in the original LSP and then to travel back in the opposite direction in the bypass tunnel. This solution is reasonable in most cases, but not bandwidth efficient in the case of ring topology.
Hence, there is a need in the art for a convenient to install, reliable, inexpensive and bandwidth efficient method for rerouting traffic in a network when a link failure occurs.